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Abstract:

A method of producing absorbent articles, comprising: suspending particles
in a gas carrier to form suspended particles; creating a series of pulses
from the suspended particles, wherein each pulse in the series of pulses
is created by: accumulating at least some of the suspended particles in a
pulsing chamber to form accumulated particles on a rotary separator, and
releasing at least some of the accumulated particles by rotating the
rotary separator to create each pulse; and suctioning each pulse from the
series of pulses onto a forming surface for the absorbent articles.

Claims:

1. A method of producing absorbent articles, the method
comprising:suspending particles in a gas carrier to form suspended
particles;creating a series of pulses from the suspended particles,
wherein each pulse in the series of pulses is created by:accumulating at
least some of the suspended particles in a pulsing chamber to form
accumulated particles on a rotary separator, andreleasing at least some
of the accumulated particles by rotating the rotary separator to create
each pulse; andsuctioning each pulse from the series of pulses onto a
forming surface for the absorbent articles.

2. The method of claim 1, wherein the creating includes:accelerating at
least some of the accumulated particles with the rotary separator to form
accelerated particles; andreleasing at least some of the accelerated
particles by rotating the rotating separator.

Description:

CROSS REFERENCE TO RELATED APPLICATIONS

[0001]This application is a divisional of prior U.S. application Ser. No.
11/493,313, filed Jul. 26, 2006, which is a divisional of U.S.
application Ser. No. 10/423,425, filed Apr. 25, 2003. This application
incorporates U.S. application Ser. No. 11/493,313 and U.S. application
Ser. No. 10/423,425 by reference.

FIELD OF THE INVENTION

[0002]The present invention provides a method and an apparatus for forming
a pulsed stream of a particulate material, allowing high pulsing
frequencies, and being particularly suitable for the production of
disposable absorbent articles, such as baby diapers and the like.

[0003]The invention is further directed to a kit or pack of individual
absorbent articles which can be produced using the method and the
apparatus.

BACKGROUND OF THE INVENTION

[0004]Creating constantly and quickly repeating pulses of particulate
material suspended in a carrier means such as air has been a long lasting
desire for many applications, in particular for pulses which are well
controlled with regard to their shape, to their frequency, and to the
amount of material transferred during these pulses. A particularly useful
application is during the manufacture of disposable absorbent articles,
such as baby diapers, adult incontinence or feminine hygiene pads, and
the like, where the manufacturing aims at high production speed and low
variability.

[0005]In U.S. Pat. No. 4,800,102 (Takada), an apparatus and method for
spraying or scattering solid particulate powders onto a substrate is
described. The powder is scattered onto a rotatable disc member, which
has at least one opening through which a portion of the powder can pass
through to reach an underlying substrate, while the non-passing powder is
recycled to the powder feeder. Another masking process is described in
PCT publication WO-A-92/19198 (Perneborn). Thereby, a device for
depositing particles on a moving web of material has an apertured belt
which moves over a material web and has a particle dispenser to dispense
particles in a uniform pattern in the shape of the apertures of the belt.
The particles not dispensed through the apertures are recycled back to
the particle feeder.

[0006]Both of these systems use the gravity for accelerating the powder
particles, and are limited in pulse frequency and hence overall
production speed. Further, as part of the powder delivered to the device
is recycled, there is only limited control of the amount of powder
disposed on the substrate, and hence in the produced article.

[0007]U.S. Pat. No. 5,213,817 (Pelley) describes a powder spray ejector
oscillating over a flow separator, which separates a portion of the
powder being deposited on a web, and the other portion being recycled.

[0008]Other approaches use pulsing of an air stream to create a pulsed
particle stream, such as described in U.S. Pat. No. 4,927,346 (Kaiser),
U.S. Pat. No. 6,033,199 (Vonderhaar). In U.S. Pat. No. 5,028,224 (Pieper)
an apparatus and process for providing a pulsed particle stream is
described, wherein a continuous gas entrained stream of particles is
centrifugally diverted into an accumulation region, from where it is
selectively discharged, such as by the use of a pulsed air stream.

[0009]U.S. Pat. No. 4,543,274 (Mulder) discloses a powder spray gun
wherein high velocity air is said to impact powder entrained air
contained in the bore of the gun. U.S. Pat. No. 4,600,603 (Mulder)
discloses a powder spray gun apparatus wherein an inverted flow amplifier
is located adjacent to the inlet of the gun to enhance blending of powder
within the gun. From the inverted flow amplifier, the blended powder is
supplied to a downstream air flow amplifier which is operable to impact
air entrained powder with a high velocity stream of compressed air. A
powder control system controls powder supply from powder supply pumps to
the spray gun. The powder pumps are said to be conventional venturi
powder pumps.

[0010]U.S. Pat. No. 4,770,344 (Kaiser) discloses a powder spraying system
including a volumetric or gravimetric material feeding device for
metering a quantity of powder into a manifold, and air flow amplifiers
connected to passageways formed in the manifold. Kaiser '344 teaches that
a problem associated with venturi powder pumps is the difficulty in
obtaining a consistently accurate feed rate of powder material,
especially when a spray gun is operated intermittently. U.S. Pat. No.
4,927,346 and U.S. Pat. No. 5,017,324 (Kaiser) disclose additional
embodiments for depositing particulate material into a pad with a spray
gun, including an embodiment having an inverted flow amplifier and an
embodiment having a rotating screw for providing a metered quantity of
absorbent particles. U.S. Pat. No. 5,037,247 (Kaiser) discloses a powder
pumping apparatus having a venturi passageway and an air ejector
including a valve mechanism. Kaiser '247 teaches that it is desirable to
include a valve in the air ejector to eliminate the "dead zone" in the
air supply tube extending between the valve and the inlet to the pump
body, and thereby eliminate the powder pulse "tailing effect" experienced
in other powder pump designs. However, such an arrangement has the
disadvantage of a requiring a valve assembly adjacent to or within the
ejector, which may not be practical or even possible in every
installation due to space or geometry constraints. These approaches have
in common, that they primarily create a pulsed gas/air stream, which
accelerates the particles to create a pulsed particle stream. However,
such air pulses are difficult to control in stable manner, in particular
for higher pulse frequencies and higher particle flow rates.

[0011]Henceforth, the present invention aims at overcoming limitations of
the known systems, in particular with regard to pulse frequency so as to
allow for higher production speeds, as well as with regard to higher
throughput on a per pad basis, so as to satisfy the requirements of
modern absorbent article design.

[0012]As a further objective the invention provides a kit or pack of
individual absorbent articles in a cost effective manner.

SUMMARY OF THE INVENTION

[0013]The present invention is a method of creating a pulsed stream of
particles in a carrier means, which includes the steps of suspending a
first metered stream of particles in a carrier means, guiding this first
stream to a pulsing means, accumulating a portion of these particles in a
pulsing chamber of the pulsing means, which further includes a separator
means, and emptying the particles out of the pulsing means by a suction
means, whereby the accumulation is performed by interrupting the stream
of particles as flowing from an inlet of the pulsing means to an outlet
of the pulsing means by the separator means for not less than 95%,
preferably not less than 90%, more preferably not less than 75% and even
more preferably not less than 50% of said time of a pulse.

[0014]Preferably, the separator means rotates in the pulsing means. It is
also preferred, that the suction means is an venturi-type ejector, or a
ring-jet-type coaxial ejector, preferably positioned in proximity to the
outlet of the pulsing means, and that the suction means is positioned in
proximity to the outlet of the pulsing means. The present invention is
particularly suitable for creating pulses at a frequency of at least 10
Hz preferably more than 15 Hz, even more preferably more than 20 Hz.

[0015]In a further aspect, the present invention is an apparatus for
pulsing a metered stream of particular material in a carrier means
comprising, a metering means, a pulsing means having an inlet, an outlet,
a pulsing chamber located there between and comprising a separator means,
and a suction means arranged in proximity of the outlet. The separator
means is arranged to interrupt said flow of particles between the inlet
and the outlet for not less than 95%, preferably not less than 90%, more
preferably not less than 75% and even more preferably not less than 50%
of said time of a pulse. The separator means may be designed to not
interrupt the flow of the carrier means, which preferably is a gas, such
as air.

[0016]It is also preferred, that the suction means is an venturi-type
ejector, or a ring-jet-type coaxial ejector, preferably positioned in
proximity to the outlet of said pulsing means, and that the suction means
is positioned in proximity to the outlet of said pulsing means.

[0017]In a further aspect the invention relates to a kit or pack of
individual absorbent articles, the absorbent articles being produced by a
method of low standard deviation manufacturing, the kit or pack of
absorbent articles comprising at least 10 individual absorbent articles
which have been produced consecutively by the method of low standard
deviation manufacturing, the absorbent articles each comprising a
topsheet and a backsheet and an absorbent core encased between the
topsheet and the backsheet, the absorbent core comprising a first
material providing for a first absorbent capacity and a second absorbent
material providing for a second absorbent capacity, the absorbent core
having a longitudinal direction, the absorbent core comprising a front
half and a rear half, the halves having equal length as measured in the
longitudinal direction, the front half of the absorbent core comprising
more than 60% of the second absorbent capacity, the second absorbent
material comprised by the absorbent material of each of the absorbent
articles having a total weight, the kit or pack of absorbent articles
having a average total weight taken as the average of the total weights
of the particulate absorbent material of individual articles, the kit or
pack of absorbent articles having a standard deviation of total weight
calculated based on the deviation of the total weight of the particulate
absorbent material of individual articles from the average total weight,
wherein the standard deviation of total weight is less than 8%.

[0020]FIGS. 3A and 3B show schematic presentations of an exemplary pulsing
means according to the invention.

[0021]FIGS. 4A through 4C show exemplary embodiments for separator means
useful in such a pulsing means.

DETAILED DESCRIPTION OF THE INVENTION

[0022]Within the context of the present description, the term "pulse" is
used to describe the time dependency of a particle flow in a certain,
repeating pattern. This pattern can be described via the local flow of
material per time interval (in units of g/sec) and a repeating frequency
defining a time interval for the pulse.

[0023]Thus, in FIG. 1A, a typical pulse pattern 100 is depicted, showing
an example for a repeating particle flow pulse. The pulse has a pulse
duration 110, a pulse repeating time period 120 (defining a pulse
frequency), and a peak pulse flow rate 130. If there is no particle flow
between two pulses, the minimum pulse flow rate 140 is equal to zero. The
particle flow can be further described by the average flow rate 135. The
particle flow can also be expressed by the particle density, defined by
the volumetric flow of particles divided by volumetric flow of air.

[0024]In particular cases, the pulse can have two (or even more) plateaus
with a second plateau flow rate 150 for a second plateau duration time
155 (see FIG. 1B), which even further may be interrupted (see FIG. 1C),
whereby a first pulse duration and frequency (145, 147) and a second
pulse duration and frequency (157, 159) can be distinguished.

[0025]The shown rectangular "pulse shape" is certainly often desired, but
generally the shape will differ to a certain extent, and in the extreme,
a can be formed by gradually increasing and decreasing flanks 170, 180
(see FIG. 1D).

[0026]Within the context of the present description, the term "flow path"
is used to describe the path of a moving object, such as a particle. A
flow path between two locations (such as cross-sectional areas 210 and
220 of a tube 200 as shown in the schematic cross-sectional view in FIG.
2) is called uninterrupted, or continuous, if a particle can move from
such a location 210 (inlet) to another location 220 (outlet) without
encountering a physical barrier, as indicated by the continuous arrows
240. It is called interrupted, if a particle is hindered by physical
barrier, such as schematically and exemplarily indicated by a rotary
valve element 230. For this instance, there will be separated flow paths
on both sides of the barrier, as indicated by the flow path arrows 245
and 247 respectively. While, of course, also movements of fluids like
gases can be described flow paths (and also both continuous as well as
interrupted ones), the term "particle" is used herein to describe
discrete solid particles, for example in the context of disposable
absorbent articles it can be absorbent particles, or superabsorbent
particles, which are essentially dry particles having a

particle size which can range from several microns to several millimetres.
Such particles can be suspended in a "carrier", such as a gas such as
air.

Description of the Features of the Process and Apparatus

[0027]The present invention is not limited to a particular application,
and flow rates, pulse frequencies can be varied in a broad range without
departing from the essence of the present invention. However, the
following explanations will refer in certain aspects to specific
examples, which will be--without limiting the present invention to this
field--the manufacture of disposable absorbent articles, such as baby
diapers and the like.

Particle Flow Metering

[0028]Metering devices to provide well defined particle mass flow rates,
in particular constant predetermined flow rates, are well known in the
art. Such a metering apparatus can include a hopper with, for example a
screw feeder and a scale or "loss-in-weight control". A suitable metering
apparatus particularly suitable in the manufacture of absorbent articles
is an Acrison Volumetric Feeder, Model No. 405-105X-F, available from
Acrison, Inc. of Moonachie, N.J. Such a metering apparatus can be
operated to provide a mass flow rate of up to about 1500 kg/hr or more,
preferably between 30 kg/hr and 1200 kg/hr.

[0029]The particle metering apparatus can be connected for further
conducting the metered particle stream to a connecting means. A typical
example for such a connecting means is a tube having an inner diameter of
about 2.5 cm (about 1 inch). Preferably, the connector means does not
have sharp edges or bends, as this might influence the stability of the
particle stream.

[0030]If the metering apparatus and the pulsing means are appropriately
arranged with regard to their relative positioning, there is no need for
a carrier means to carry the particle from the metering apparatus to the
pulsing means, but gravity would suffice to let the particles fall from
the first to the second. However, often it can be advantageous to have
some carrier flow, such as air flow. If an additional carrier stream is
used, this is preferably done at moderate carrier speed, and in a
preferred embodiment as described hereinafter, carrier velocities of
between 1 and 20 m/sec have been found to be suitable. This carrier
stream is further preferably steady to maintain a constant particle
stream. In case of carrier flow fluctuations, these are preferably in
phase with the pulsing frequency so as maintain stable conditions. For
the described exemplary application in the manufacture of absorbent
articles, such a carrier flow can be created by having an opening to the
ambient in the connecting means, positioned close to the metering
apparatus. Suction as applied on the other side of the pulsing means (and
discussed hereinafter) can suffice to provide stable particle flow
conditions.

[0031]An important element of the present invention is the pulsing means,
arranged (in following the flow path direction of particles) after the
connection means, and operated so as to create the pulsed particle flow.

[0032]The pulsing means is designed to allow interrupting the particle
flow in a repeating manner, whereby the particles are accumulated during
this interruption period and released thereafter. The pulsing means
comprises an inlet, through which the particles can enter the pulsing
means, an outlet, through which the particles can exit the pulsing means,
a pulsing chamber positioned between the inlet and the outlet providing
sufficient space to allow accumulation of at least some of the particles,
and a separator means, positioned in this pulsing chamber.

[0033]While it may interrupt the carrier flow for a part of a cycle time,
there has to be a certain time, during which the carrier flow path and a
particle flow path are connected from the inlet of the pulsing means to
the outlet of the pulsing means. Without wishing to be bound by the
explanation, it is believed, that this period is important to stabilize
the flow properties of the carrier.

[0034]A pulsing means suitable for applications such as in the production
of absorbent articles can be designed to pulse a stream of absorbent
particles, with typical sizes in the range of several micron to few
millimetres, and with particle flow rates in the range of 1500 kg/hr or
more. For such an application, pulse frequencies can range from about 3
to about 35 Hz or even more.

[0035]A suitable pulsing means in the context of the present invention
impacts on the particles directly in a valve-type function. This is to be
seen in contrast to other approaches, wherein a pulse of a carrier means,
such as a pulsed air stream, impacts on the particles. The valve
type-operation can be realized by various designs, such as oscillating
slide valves, iris-type valves, diaphragm-type valves, rotating,
apertured disks similar to the design as described in U.S. Pat. No.
4,800,102 (Takada).

[0036]A further exemplary and preferred pulsing means builds on the
principles of a rotary valve, as is well known in the art as a closure
element, such as for a storage container for particulate material.
Therein, however, they are designed to hermetically separate the storage
container from the subsequent system, such as a pneumatic transport
system, without providing a certain period of the cycle time with a
continuous particle flow path--see as one of various exemplary
disclosures U.S. Pat. No. 3,974,411 (Miller). Alternatively, rotary
valves are known to provide for an "open-close" functionality (i.e. no
accumulation functionality as in the present case), such as described in
U.S. Pat. No. 4,393,892 (Di Rosa).

[0037]One particular benefit of such rotary designs is the avoidance of
oscillatory movements, which, in particular for higher frequencies, would
create either undesirably heavy (and hence difficult to accelerate)
elements, or designs with a non-satisfactory reliability. In contrast to
these, a rotary design can keep the separator means operating at a
constant speed, thus allowing a much more stable operation even for high
pulse frequencies.

[0038]As depicted in a schematic, cross-sectional view--see FIG. 3A--such
a preferred rotary pulsing means 310 can comprise a rotating separator
means 330, rotatably mounted in a pulsing chamber 320, having a
cylindrical shape with a diameter and a height, of the pulsing means 310.
Further indicated is a particle flow path 370, freely connecting the
inlet 340 and the outlet 350, without being obstructed by a separator
means 330. FIG. 3B schematically shows the same equipment (with equal
numerals indicating same elements), now at a different rotational
position of the separator means 330, such that there is no free particle
path connection between the inlet 340 and the outlet 350, but there is a
filling flow path 372 disconnected from the emptying flow path 374.

[0039]When, during the operation, the separator means 330, as it rotates
at a predetermined frequency, it takes the position of interrupting the
particle flow path, the particles, arriving at the inlet 340 at an
essentially constant stream will accumulate in that part of the pulsing
chamber 320, which is connected to the inlet 340. During this time,
essentially no particles will exit the pulsing means through the outlet
350. During the period where the separator means 330 is in a position so
as to not interrupt the particle flow path, the chamber will essentially
be emptied, and some particles may penetrate through the complete
chamber, depending on the relative speed of the particles compared to the
rotational speed. If these speeds are appropriately chosen, the rotation
of the separator means can impact on the accumulated particles and
accelerate these out of the chamber.

[0040]For the exemplary application in the production process of
manufacturing disposable absorbent articles, the diameter of the pulsing
chamber can suitably be in the range of 50 to 500 mm, with a diameter of
120 mm working well. The thickness dimension (i.e. along an axis
perpendicular to the plane of FIG. 3) can suitably be in the range of
about 10 to about 100 mm, with a thickness of 50 mm found to be working
well.

[0041]For a symmetrically shaped separator means 330 as indicated in FIG.
3, one 360° rotation of the separator means will result in
creating two pulses, i.e. the pulse frequency is twice the rotational
frequency.

[0042]The separator means 330 can be an essentially rectangular bar with
its ends being rounded to fit smoothly into the cylindrical separator
chamber without undue friction or gapping. The separator means can also
have different shapes, provided it enables the separation function by
smoothly fitting to the walls of the separator chamber. For example, it
can have essentially oval cross-section, or ellipsoidal shape, or others
as indicated in FIG. 4 A to C (see separator means 430a-430c). The shape
of the separator means can be used to design the shape of the resulting
pulses, in particular to create stepped pulses, or two subsequent pulses
with differing pulse form. An asymmetric design of the separator means
results in two pulses per one 360° rotation of the separator
means, each with a different pulse shape. FIG. 4B shows an essentially
semi-circular cross-section. Such a design would provide one accumulation
phase for one rotation of the separator means.

[0043]While in FIGS. 2 and 3 the inlet and the outlet have been shown in a
particular relative positioning (in a 180° degree arrangement),
this does not need to be the case. It will be clear to a skilled person
that the relative positioning of inlet and outlet to each other will
impact on the pulse shape in cooperation with the shape of the separator
means. Thus, for many applications, the 180° design will be most
suitable, but this does not need to be always the most preferred
execution. Also, for the inlet and the outlet duct there does not need to
be a radial arrangement of the connector means (as shown in FIGS. 2 and
3), but more tangential or even curved tangential designs can be
preferred. It has been found that more tangential outlet could deliver a
significantly higher throughput of particles compared to a perpendicular
outlet. Similarly, the size of the inlet and outlet openings can be
equal, such that the projected area ratio of the two is about one. A
skilled person will readily find out the balance of simplicity of design,
match with other fittings of the apparatus, and, of course, the desire
for maintaining the pulse shape adequately.

[0044]In order to transfer the particles from the pulsing chamber to the
further steps of the process, suction is applied to empty the pulsing
chamber effectively. In the exemplary process of manufacturing absorbent
articles, the forming of such articles often comprises the step of laying
down absorbent materials--such as the particles undergoing the pulsing
step--on a forming means, such as a permeable carrier, by applying vacuum
on the side facing away from the feeding and pulsing means. Then, this
vacuum can suffice to create suction for emptying the separator chamber,
and an opening positioned close to the outlet of the pulsing chamber can
provide sufficient carrier flow.

[0045]Under certain conditions it will be desired to not only empty the
pulsing chamber quickly, but also to accelerate the particles to a
relatively higher speed. Such instances can be for example the mixing of
these particles with other matter, such as fibres, like cellulose fibres,
staple synthetic fibres meltblown fibres or the like, in the case when
forming absorbent articles. Such acceleration should preferably not
distort the pulse shape as created by the pulsing means. Then, a
particular suction means can be positioned between the pulsing chamber
and the forming means.

[0046]It is important, that the suction means does not distort the shape
of the pulse too much, such as for example a rotary ventilator would do.
It has been found suitable to use an additional stream of carrier, such
as gas or air, so as to accelerate the carrier stream and thereby also
the particle pulse stream. A venturi type ejector has been found suitable
if used to provide moderate suction and hence acceleration. For higher
suction and acceleration, such venturi type ejectors tend to provide a
non-uniform flow pattern across the cross-section, generally in the shape
a pronounced parabolic profile. However, in order to maintain the shape
of the pulse, a more rectangular, or "plug flow" profile is preferred.

[0047]A suitable element to provide such flow characteristics has been
found in a coaxial eductor. Two design principles have been found to be
particularly suitable each for certain circumstances:

[0048]a) A ring jet ejector, which use is based on the well known Coanda
effect, has been found to be working extremely well especially for lower
particle density streams (i.e. lower average particle flow rates) which
need to get accelerated to very high speeds. This is due to the fact that
Coanda effect based ejector designs deliver the highest suction air
volume stream at least for carrier-only systems. Coanda flow tends to
stall if the particle density is too high. [0049]The design of these
ejectors even more preferably has a fixed gap design. Such ejectors can
be produced by EXAIR (Cincinnati, Ohio, USA) under the designation Air
Amplifier 6032, or Krahnen (Cologne, Germany) under the designation RJ25.
It has further been found, that such ejectors can provide velocities of
the carrier of up to of 80 m/sec or even more with a much more levelled
velocity profile.

[0050]b) A coaxial ejector designed to use the Venturi effect has been
found to be less critical to higher particle densities (volumetric flow
of particles divided by volumetric flow of air). Such ejectors still
deliver plug flow type of speed profiles, which preserve the pulse, as
delivered from the separator mean. Such ejectors can be produced by EXAIR
(Cincinnati, Ohio, USA) Line Vac 6063. These devices may need
modification to increase suction air by increasing the motive air, such
as by increasing the number of air throughput holes.

[0051]A particular benefit of such an arrangement is, in addition to
providing a sharply defined pulse, an even profile throughout this pulse.
In particular, it allows avoiding of a bias in the profile, such as a
particle distribution to the left or right side of a system.

[0052]In order to allow a more effective emptying of the pulsing chamber,
the suction means is preferably positioned in the proximity of the outlet
of the chamber, more preferable immediately adjacent thereto. To change
the profile this may be changed according to the application need i.e.,
if the slope of the density change should be less steep a longer distance
would be appropriate.

[0053]Once the pulsed particle stream has been created, and optionally
accelerated, the transfer to the downstream process steps can be done in
any conventional manner as well know to the skilled person, and as
described in the above referenced documents. As indicated in the above,
such process steps can include mixing of the pulsed particle stream with
other materials, such as in the exemplary application of forming
absorbent articles with fibres, which can be a continuous stream, or
discontinuous. The pulsed stream can also be laid down on a forming
means, such as a screen or web permeable to the carrier but not to the
particles. Preferably, the distance to the subsequent process steps is
not too long so as to allow maintaining the pulse shape.

Preferred Products and Kits or Packs of Products

[0054]Preferably the method of creating a pulsed stream of particles is
used for the production of absorbent articles, such as baby diapers,
training pants, adult diapers or incontinence products, sanitary napkins
and the like.

[0055]These articles are known to typically comprise a topsheet, facing
the wearer when the article is used, and a backsheet. Topsheet and
backsheet are typically joined and encase the absorbent core.

[0056]The absorbent core may comprise any absorbent material that is
generally compressible, conformable, non-irritating to the wearer's skin,
and capable of absorbing and retaining liquids such as urine and certain
other body exudates. The absorbent core may comprise a wide variety of
liquid-absorbent materials commonly used in disposable diapers and other
absorbent articles such as comminuted wood pulp, which is generally
referred to as air felt. Examples of other suitable absorbent materials
include creped cellulose wadding; melt blown polymers, including co-form;
chemically stiffened, modified or cross-linked cellulosic fibers; tissue,
including tissue wraps and tissue laminates; absorbent foams; absorbent
sponges; superabsorbent polymers; absorbent gelling materials; or any
other known absorbent material or combinations of materials.

[0057]Preferred absorbent cores according to the present invention
comprise a first material providing for a first absorbent capacity and a
second absorbent material providing for a second absorbent capacity.
Preferably the first material is a fibrous absorbent material and the
second absorbent material is a particulate absorbent material and most
preferably a superabsorbent material. Most preferably the fibrous
material has a substantially uniform basis weight over the whole area of
the core. If the core comprises fibrous layers which do not comprise
superabsorbent material, e.g., do serve for example as acquisition or
distribution layers, the basis weight of these layers does not need to be
uniform, and it is preferred that only those fibrous layers which serve
as containment means for superabsorbent material have uniform basis
weight.

[0058]In another embodiment of the present invention the first material is
not an absorbent material, i.e., its absorbent capacity is zero or
essentially zero. Such a material can serve to maintain the structure and
integrity of the absorbent core. For example it can be an adhesive
material.

[0060]Preferred articles according to the present invention achieve a
relatively narrow crotch width, which increases the wearing comfort. A
preferred article according to the present invention achieves a crotch
width of less than 100 mm, 90 mm, 80 mm, 70 mm, 60 mm or even less than
50 mm.

[0061]Absorbent articles are typically marketed in kits or packs
comprising multiple individual absorbent articles, for example at least
10, 12, 15, 20, 25 or 30 individual absorbent articles are sold together.
Consumers expect each individual absorbent article to deliver the same
satisfying performance, namely in respect of absorbency. It is most
critical to provide sufficient absorbency in the front half of the
articles. The front half of the article is typically the area to receive
discharged urine, which is then to be stored in the front half of the
absorbent core.

[0062]The front half of the absorbent core should therefore comprise most
of the absorbent capacity of the core. Preferably most the absorbent
capacity of the core comprising a first and a second absorbent material
is provided by the second absorbent material, which is preferably a
particulate material and most preferably a particulate superabsorbent
material. Preferably, the front half of said absorbent core comprises
more than 60% of the absorbent capacity of the second absorbent material,
more preferably more than 65%, 70%, 75%, 80%, 85%, 90% or 95%.

[0063]As consumers expect each individual absorbent article to deliver the
same satisfying performance, but as on the other hand absorbent materials
and in particular superabsorbent materials are costly, it is desirable to
provide a kit or pack of individual absorbent articles wherein each
individual absorbent article comprises about the same amount of absorbent
materials and in particular superabsorbent materials.

[0064]An appropriate measure for the amount of absorbent material is the
total weight of the absorbent material. It is desirable that the total
weight of the absorbent material and namely of superabsorbent material in
each individual absorbent article in a kit or pack is about the same as
the average total weight of that material in the kit or pack. In other
words, the standard deviation of the total weight of that material should
be low. It is preferred that the standard deviation of total weight is
less than 8% or less than 7%, and preferably less than 6%, and yet
preferably less than 5%, and yet preferably less than 4%, and yet
preferably less than 3%, and yet preferably less than 2%.

[0065]The disclosed process enables to produce kits or packs of absorbent
articles with very uniform distribution of the amount of superabsorbent
material.

[0067]The present invention allows to achieve the above standard
deviations where fast processes of manufacturing are employed. The above
standard deviations can achieved at a production lines yielding more than
100, 200, 300, 400, 500, or even more than 600 absorbent articles per
minute.

[0068]These articles are typically produced in a process of low standard
deviation manufacturing for consecutive production of many absorbent
articles. Not all article produced in such process may meet the desired
quality standards. Some articles may be considered faulty and are
therefore either manually or automatically excluded from being sold to a
consumer and e.g. not packed. If, for example, eleven or twelve articles
are produced and one or two articles are considered faulty, the remaining
ten articles are herein considered to be consecutively produced.

[0069]All documents cited in the Detailed Description of the Invention
are, in relevant part, incorporated herein by reference; the citation of
any document is not to be construed as an admission that it is prior art
with respect to the present invention.

[0070]The dimensions and values disclosed herein are not to be understood
as being strictly limited to the exact numerical values recited. Instead,
unless otherwise specified, each such dimension is intended to mean both
the recited value and a functionally equivalent range surrounding that
value. For example, a dimension disclosed as "40 mm" is intended to mean
"about 40 mm."

[0071]Every document cited herein, including any cross referenced or
related patent or application, is hereby incorporated herein by reference
in its entirety unless expressly excluded or otherwise limited. The
citation of any document is not an admission that it is prior art with
respect to any invention disclosed or claimed herein or that it alone, or
in any combination with any other reference or references, teaches,
suggests or discloses any such invention. Further, to the extent that any
meaning or definition of a term in this document conflicts with any
meaning or definition of the same term in a document incorporated by
reference, the meaning or definition assigned to that term in this
document shall govern.

[0072]While particular embodiments of the present invention have been
illustrated and described, it would be obvious to those skilled in the
art that various other changes and modifications can be made without
departing from the spirit and scope of the invention. It is therefore
intended to cover in the appended claims all such changes and
modifications that are within the scope of this invention.